In 1480 he was appointed dean of the Faculty of Theology at the University. His lecture room was thronged and the following year he was appointed Inquisitor for the Provinces of Mainz, Trier and Cologne. His activities in this post demanded constant travelling through the very extensive district.[1]

It has been claimed that Sprenger was not interested in witches and that he cannot be linked to any witch trial. His personal relationship to Kramer was acrimonious and Sprenger used his powerful position whenever he could to make Kramer’s life and work as difficult as possible.[4] Scholars now believe that he became associated with the Malleus Maleficarum largely as a result of Kramer's wish to lend his book as much official authority as possible.[5]

^A work from 1719 reports that Sprenger was known in the Dominican house for "his burning and fearless zeal for the old faith, his vigilance, his constancy, his singleness and patience in correcting novel abuses and errors."

^The Catholic Encyclopedia states Innocent's Bull enacted nothing new. Its direct purport was simply to ratify the powers already conferred upon Henry Institoris (i.e. Heinrich Kramer) and Jacob Sprenger, inquisitors, to deal with persons of every class and with every form of crime (for example, with witchcraft as well as heresy), and it called upon the Bishop of Strasburg to lend the inquisitors all possible support."Witchcraft". Catholic Encyclopedia. New York: Robert Appleton Company. 1913.